Soooo many questions..
Firstly what sort of metrics do you use to show someone performs better in work than at home? Since everyone has an infinite variable set of circumstances, I can't think of an easy way to measure it.
For example if you a women with 3 kids, are you more productive being dragged into the office to do a job you are quite capable of doing just as well at home?
There are however other metrics that can be measured such as the number of sick days taken. These are rarely mentioned in these arguments, but the fact it is easier to work from home when feeling slightly ropey and you are not a walking virus cloud in the office would suggest that sickness leave would be reduced. Then there is productivity. People working from home will start earlier and work later because they don't have the daily commute, never mind they can integrate there life around work rather than sneaking off because their kids are sick and all holiday has been used.
Yes the argument about creating connections is an important one, but not everyone is the same. People of a certain generation are quite happy with virtual links, and can adapt well (You would of thought a social media site would understand this)
However the main thing we find with hybrid working rules is how unevenly the rules are applied. Workers are told to get back into the office, while managers will always find an excuse to work from home (important call, etc)
At the end of day, the problem is not productivity it is the sight of empty expensive real estate that is the primary driver. Only time will fix that